A booster, or a pneumatic servomotor for an assisted braking, comprises a rigid jacket, made up of two shells forming, on the one hand, the cover and, on the other hand, the cylinder, which are assembled by crimping. Inside the jacket of the pneumatic servomotor for an assisted braking, a variable-volume front chamber is separated from a variable-volume rear chamber by a tight flexible diaphragm and by a rigid skirt driving a pneumatic piston which bears, through a control rod, on the primary piston of a tandem master cylinder of a hydraulic braking system. The front chamber, directed towards the tandem master cylinder, is hydraulically connected to a vacuum source whereas the rear chamber is hydraulically connected, using a valve control, to a propellant fluid source, typically atmospheric-pressure air.
In this type of servomotors, it would be useful to carry out a measurement of the force exerted on the control rod of said pneumatic servomotor for an assisted braking, on actuation, and to transmit such information to a processing unit so as to supply the braking system with input data regarding the force, which is actually applied to the brake. In the same way, it would be a good thing to be able to measure such forces in a master cylinder, directly connected to the brake pedal.
The travel of the pedal on the actuation of the brake, should also be determined.
Generally, one uses, on the one hand, a force sensor for the control rod and, on the other hand, in the case of a servomotor, the pneumatic piston as a test body of an eddy-current stroke sensor and, insofar as a master cylinder is concerned, the primary piston is used for this purpose.
Yet, a stroke sensor plus a force sensor make the structure heavier and more intricate.